Traditionally, the polyester repair markets have utilized well-defined processes in the area of damage repair. Unsaturated polyester resins, primers, fillers, adhesives, or putties are used to resurface and reshape damaged areas. For ease of understanding, the term “resin” will be used in the following description; however, it is to be understood that the term includes cured resins and prepolymers (uncured resins), primers, fillers, adhesives, and putties. The method for catalyzation and application of the resin is as much an art as it is a science. This is due in part to the very small amount of peroxide hardener (catalyst) that is used to cure the much larger amounts of unsaturated polyester resin properly. The optimum peroxide level needed to cure the resin is generally about 1 to 3 parts per hundred of the resin by weight. The resin and peroxide are packaged in separate containers, typically a large can for the filler (8 oz. to 55 gal.), and a small tube for the peroxide catalyst (0.25 oz. to 4 oz.).
The user dispenses a variable amount of resin into a cup or onto a mixing board, and adds the peroxide catalyst, essentially guessing at the correct amount for proper catalyzation. The consequences of improper catalyzation of the resin include loss of adhesion to the substrate, uncured surface (tacky), cracking of the resin due to excessive heat generation, migration of uncured resin organics to subsequent coatings resulting in discoloration of top coats, outgassing of uncured material in the presence of ultraviolet or heat energy from sunlight or paint baking systems resulting in blistering and other damage to the topcoat, as well as other problems that may require removal and replacement of the repair.
Efforts have been made to provide controlled metering of the peroxide to ensure that the proper amount is mixed with the thermoset resin. Because many commercially available peroxide solutions have a viscosity similar to water, dispensing in a mechanical metering system was difficult in non-spray applications. As a result, there has been an attempt to develop a thicker, more controllable gel or paste form of the organic peroxide.
The standard benzoyl and ketone peroxides use plasticizers such as phthalates as carriers. U.S. Pat. No. 5,880,181 describes a gel comprising A) a solution of at least one organic peroxide essentially solubilized in a phlegmatizer, B) at least one cellulose ester as thickening agent essentially solubilized in solution A, and C) at least one thixotropic agent selected from hydrogenated castor oil and fumed silica. The phlegmatizer is selected from the group consisting of phthalates, glycols, citrates, benzoates, phosphates, adipic acid ester, glutaric acid ester, maleic acid ester, fumaric acid ester, succinic acid ester, butyrates, and mixtures thereof.
However, plasticizers and phlegmatizers are non-reactive. The non-reactive nature of the carrier does not adversely affect performance of the cure at levels of 1.5 to 3 parts per hundred unsaturated resin, but levels above 5 parts per hundred can disrupt the cure.
There remains a need in the art for a peroxide catalyst that can be easily metered and which will not disrupt curing of the resin.